Information is often grouped on recording tapes in the form of exercises. These exercises are distinguished from each other by blank spaces on the tape, or by distinctive tones at the beginning of each exercise, or by address information at the beginning of each exercise. The grouping of information on tapes into exercises allows great versatility to the user of the tape by providing a mechanism adaptable to skip back and forth to desired exercises or segments thereof.
Many prior art arrangements have been developed to indicate the beginning of exercises for use with "repeat" and "skip" features. In the "repeat" feature, the depression of a repeat key or other switch causes the tape player to rewind the tape to the beginning of the instant exercise and then to play back the tape at the normal forward speed. In the "skip" feature, the depression of a skip key or similar switch causes the tape to assume a fast-forward mode until the next exercise is reached at which time the tape returns to its normal playback speed.
In one prior art end-of-message-detection arrangement, small holes were provided in the tape at the end of each message and a brush was provided to engage a contact through the tape when a hole passed in front of the brush. This appears to be a usable arrangement; however additional "end-of-message" detection equipment is required and, moreover, it is believed to be commercially difficult to mass-produce tapes having holes at the appropriate places therein.
In another prior art arrangement, a constant out-of-band tone was provided with the message, and separations between messages were left completely blank. Thus in this arrangement the failure to detect the out-of-band tone indicated the beginning of a message. Utilization of this arrangement may require expensive high quality tape without the normal oxide deformities found on regular grade tape.
In still another prior art arrangement, a two-channel tape was provided in which a distinctive tone was placed on one channel of the tape -- only at the end of each exercise. A tone detector detected this distinctive tone and was adapted to increment an up-down counter each time one of these distinctive tones was encountered during playback. This counter was also adapted to decrement its count each time one of these distinctive tones was encountered during rewinding. The operator of the system stopped the rewinding when the counter reached the desired count, normally 0, indicating the beginning of the instant message. This arrangement appears to be effective; however, one channel of the tape is dedicated to provide end-of-message information, and additional circuitry is required to detect the end-of-message indications and control the counter.
In another prior art arrangement, a tape information system is disclosed in which short silent periods are provided between each message and in which circuitry is adapted to detect these silent periods to disengage the tape transport from either a fast-forward or rewinding mode. This arrangement too appears to be efficient; however, it may be desirable to include silent periods within messages, particularly in training environments in which, during a message, time must be provided for the user to complete the functions specified by a portion of the message.
Still another prior art arrangement discloses an audio tape information system utilizing a two-channel tape. Message and address information are provided on one channel while START and STOP indications for each of the messages are provided in corresponding positions on the other channel. The user is able to select the address of the next message and, accordingly, may skip to any message on the tape as indicated by the address information thereon. Circuitry is provided to count the number of end-of-message indications encountered on the tape during playback to indicate the address of the instant message. This address is compared with the desired address and, when a match occurs, the tape is stopped.
It is an object of this invention to detect signals on a recording tape during fast forward or rewind speeds while minimizing the circuitry and information on the tape dedicated to this function.
It is a further object of this invention to detect such signals over wide variations in the repeat of fast-forward speeds.